1. Field of the Disclosure
The present invention relates generally to circuits that drive light emitting diodes (LEDs). More specifically, the present invention relates to circuits that LED driver circuits that may include dimming circuitry.
2. Background
As light emitting diode (LED) lighting becomes more affordable and increases in popularity, many LED light sources are to be replacements for traditional incandescent light bulbs. Accordingly, these LED light sources designed to be compatible with in existing sockets that were originally designed to work with conventional incandescent light bulbs. Many ac/dc LED driver circuits are designed to operate and drive the LED light sources when supplied from an ac source. Sometimes, the existing light switches used to turn on and off the lights include a dimming circuit, such as a triac. Thus, the ac source supplying power to the LED driver circuit may be connected or disconnected from the input of the LED driver circuit by a user with an ordinary on/off switch, or the supply of power from the ac source may also be controlled electronically with the dimming circuit, such as a triac.
A triac generally dims the light from an incandescent light bulb by varying the percentage of time, or the portion of each ac half cycle of an ac input signal, that is removed from an ac input signal supplying power to the incandescent light bulb.
In response to a triac varying the percentage of time, or portion of each ac half cycle that is removed from the ac input signal supplying power to the LED driver circuit, the LED driver circuit can be configured handle this circumstance in a variety of ways. For instance, the LED driver circuit can be designed to be unresponsive to the variation in the ac input signal caused by the triac. In the alternative, the LED driver circuit may also be configured so that the output of the LED driver responds to the variation for example by varying the LED driver circuit output voltage and or current. If the LED driver circuit output voltage or current is reduced as the percentage of the mains cycle for which the ac source is disconnected from the input to the LED driver circuit is increased, the result will be a form of dimming of the LED light output. This could be deigned to look like the dimming of a normal incandescent bulb.